Outbreaks of canine visceral leishmaniasis in Oklahoma and Kansas increase the risk of potential human cases within the continental United States. Despite the long established association between human kala-azar and canine reservoir infections, many questions remain concerning leishmaniasis in the dog. Of particular interest are the ability of the dog to transmit infection during the long incubation period and the clinical alterations which occur during this period which may allow for an earlier diagnosis of the disease. This study will trace the time course of parasite metastasis following an intradermal inoculation of Leishmania sp. (Oklahoma strain) and Leishmania chagasi organisms into the dog. An attempt will be made to correlate levels of infection with the clinical, immunologic, hematologic and pathologic alterations in the host during the entire course of the disease. In addition, studies will be undertaken to examine the possible role of oral and congenital transmission of Leishmania parasites in the canine host. Clinical studies will emphasize the pathogeneses of blood, renal, cutaneous and immune system pertubations which mimic infection in man and will provide an experimental basis for utilizing the dog as a model for human kala-azar. In addition to canine studies, the potential of cats and equines to act as reservoirs for leishmanial infections will also be investigated. Anecdotal reports of infection with Leishmania spp. do exist in these animals, and the discovery of Leishmania-specific antibody titers in a horse and cat in Oklahoma suggest contact with the parasites. Experimental studies with Leishmania sp. (Oklahoma strain) will establish the susceptibility of these animals to leishmanial infections and determine their potential to act as a source of parasites for transmission to humans.